1. Field of the Invention
The present invention relates to an electric circuit apparatus formed by electrically connecting electric circuit components with an electrically connecting member.
2. Related Background Art
Hitherto, known techniques for electrically connecting electric circuit components are exemplified by:
(1) wire bonding method, PA1 (2) TAB (Tape Automated Bonding) method (for example, an art disclosed in Japanese Patent Laid-Open No. 59-139636), PA1 (3) CCP (Controlled Collapse Bonding) method (for example, see Japanese Patent Publication No. 42-2096 and Japanese Patent Laid-Open No. 60-57944), PA1 (4) The art shown in FIGS. 1 and 2, PA1 (5) The art shown in FIG. 3, and PA1 (6) The art shown in FIG. 4.
The art shown in FIGS. 1 and 2 is characterized in that:
an insulating film 71 made of polyamide or the like is formed in the portions except for conjunction portions 5 of a first semiconductor deice 4. Metal members 70 made of Au or the like are provided for the conjunction portion 5 before flattening exposed surfaces 73 and 72 of the metallic members 70 and the insulating film 71. On the other hand, another insulating film 71' made of polyamide or the like is formed in the portions except for conjunction portions 5' of a second semiconductor device 4'. Metal members 70' made of Au or the like are formed in the conjunction portion 5' before flattening exposed surfaces 73' and 72' of the metal members 70' and the insulating film 71'.
Then, the first semiconductor device 4 and the second semiconductor device 4' are, as shown in FIG. 2, positioned and welded so that the conjunction portions 5 of the first semiconductor device 4 and the conjunction portions 5' of the second semiconductor device 4' are connected to each other with the metal members 70 and 70'.
The method according to (5) and shown in FIG. 3 is characterized in that:
an anisotropic conductive film 78 is interposed between a first circuit substrate 75 and a second circuit substrate 75', this anisotropic conductive film 78 being formed by having conductive particles 79 dispersed in an insulating material 77. The first and second circuit substrates 75 and 75' are then positioned before application of a pressure alone or a combination of a heat and pressure whereby a junction portion 76 of the first circuit substrate 75 and a junction portion 76' of a second circuit substrate 75' are connected to each other.
The method according to (6) and shown in FIG. 4 is characterized in that:
an elastic connector 83 designed such that metal wires 82 disposed in an insulating material 81 are formed of Fe or Cu and arranged in the same direction and interposed between the first circuit substrate 75 and the second circuit substrate 75'. The first circuit substrate 75 and the second circuit substrate 75' are then positioned before being pressurized whereby the conjunction portion 76 of the first circuit substrate 75 and the conjunction portion 76' of the second circuit substrate 75' are connected to each other.
However, the above-described conventional bonding method involves the following problems:
a circuit design based on the bonding method involves a certain limitation. The pitch (the distance between the central portions of the neighboring junctions) between the neighboring conductors is too large, and the overall thickness of the circuit cannot be reduced. In addition, the reliability is insufficient because of corrosion and breakage of the conductor, and the characteristics can deteriorate due to the concentration of heat in the portions between the bonding members and the electric circuit members. Furthermore, if an electric circuit part becomes defective, it cannot be solely replaced.
The art shown in FIGS. 1 and 2 has the following problems:
(a) The exposed surface 72 of the insulating film 71 and the exposed surface 73 of the metallic members 70 or the exposed surface 72' of the insulating film 71' and the exposed surface 73' of the metallic member 70' needs to be flattened. Therefore, its manufacturing cost will rise due to increase in the manufacturing process.
(b) If there were any differences in levels between the exposed surface 72 of the insulating film 71 and the exposed surface 73 of the metallic members 70 or between the exposed surface 72' of the insulating film 71' and the exposed surface 73' of the metallic member 70', the metallic members 70 and 70' cannot be properly connected to each other, reducing the reliability of the electric circuit.
The art according to (5) and shown in FIG. 3 has the following problems:
(a) When the conjunction portions 76 and 76' are connected to each other by application of a pressure after they have been positioned, the connected portions become unequal since the pressure cannot be applied equally. As a result, the resistance of the conjunction portions caused from contact also becomes unequal. This leads to the deterioration in the reliability in the connection. In addition, if a large amount of electric current is allowed to pass through the circuit, the junction portions adversely generate heat. Therefore, this art cannot be suitably used in a case where a large amount of electric current is intended to be allowed to pass.
(b) Even if a pressure is applied equally to the conjunctions portions 76 and 76', the resistance distribution becomes unequal due to the configurations of the conductive particles 79 of the anisotropic conductive film 78. It leads to the deterioration in the reliability in the connection established. In addition, this art cannot be suitably used in a case where a large amount of electric current is intended to be allowed to pass.
(c) Since the resistance between the neighboring conjunction portions can be reduced by shortening the pitch between the neighboring conjunction portions (the distance between the center portions of the neighboring conjunction portions), it is not suitably used in dense connections.
(d) Since the resistance can be varied by the unequal projection h.sub.1 of the conjunction portions 76 and 76' of the circuit substrates 75 and 75', the unequal projections h.sub.1 must be restricted.
(e) Furthermore, if the anisotropic conductive film were employed to connect the semiconductor devices and the circuit substrate or to connect the first semiconductor devices and the second semiconductor devices, a bump needs to be provided for each conjunctions portion of the semiconductor device, causing the overall cost to be raised.
In addition, when the art according to (6) and shown in FIG. 4 is employed to connect semiconductor devices and a circuit substrate or to connect the first semiconductor devices and the second semiconductor devices, the following problems (a) to (d) arise: (a) Since pressure needs to be applied to the conjunction portions, a pressurizing tool needs must be used. (b) Since the contact resistance between the metal wire 82 of the elastic connector 83 and the conjunction portion 76 of the first circuit substrate 75 and the conjunction portion 76' of the second circuit substrate 75' can be varied due to the pressure applied and the surface condition, the reliability of the connection is insufficient.
(c) Since the metal wire 82 of the elastic connector 83 is made of a rigid material, each surface of the elastic connector 83, the first circuit substrate 75, and the second circuit substrate 75' can be damaged if the applied pressure is too large. On the other hand, if the applied pressure is too small, the reliability of the connection is also insufficient.
(d) In addition, the projection h2 of the conjunction portions 76 and 76' of the circuit substrate 75 and 75', the projection h3 of the metal wire 82 of the elastic connector 83, and their uneveness can cause changes in the resistance and damage. Therefore, countermeasures for reducing the uneven projections must be taken.